In recent years, technologies have been developed that make clear relationships among large amounts of information in society, which is called BIG DATA. As the most basic method of making clear the relationships among large amounts of information, for example, there is a technology that is disclosed in PTL 1. In PTL 1, a user set S is specified, a network diagram is created by calculating similarities among user sets S, and the relationships among the user sets are visualized.
Furthermore, in PTL 2, as a technology that reduces the time taken to calculate a correlation coefficient, a technology is disclosed that shortens the time taken to calculate a correlation coefficient by limiting a region that is used for correlation calculation and obtaining the correlation coefficient without using all pieces of data among the variables.